<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, initial-scale=1.0">		
		<title></title>
		<link rel="stylesheet" href="./Bootstrap4.6.1/css/bootstrap.css">
		<script src="./Bootstrap4.6.1/js/jquery.js"></script>
		<script src="./Bootstrap4.6.1/js/bootstrap.bundle.js"></script>
		<style>
			span{
				margin-top: 3rem;
				margin-left: 1rem;
				display: inline-block;
				width: 100px;
				height: 100px;
				
			}
			
			.bg{
				background-color: red;
			}
		</style>
		
	</head>
	<!-- 
	 推荐用工具类的场景：1、在设置响应式样式的时候；如大屏有外边距，小屏没有外边距
						2、只给个别标签加相应的样式的时候
	不推荐使用场景：给10个以上标签加同样的样式的时候
						
	 -->
	<body>
		<div class="container border">
			<span class="border">aaa</span>
			<span class="border-top">bbb</span>
			<span class="border-right">ccc</span>
			<span class="border-bottom">ddd</span>
			<span class="border-left">fff</span>
			
		</div>
		
		<div class="container">
			<span class="border border-0">001</span>
			<span class="border border-top-0">002</span>
			<span class="border border-bottom-0">003</span>
			<span class="border border-left-0">004</span>
			<span class="border border-right-0">005</span>
		</div>
		<div class="container">
			<span class="border border-primary">001</span>
			<span class="border-top border-success">002</span>
			<span class="border-bottom border-danger">003</span>
			<span class="border-left border-warning">004</span>
			<span class="border-right border-info">005</span>
		</div>
		<div class="container">
			<span class="bg rounded"></span>
			<span class="bg rounded-top"></span>
			<span class="bg rounded-circle"></span>
			<span class="bg rounded rounded-0"></span>
			<span class="bg rounded-lg"></span>
			<span class="bg rounded"></span>
			<span class="bg rounded-sm"></span>
			
			
		</div>
	</body>
</html>